The biosynthesis of epidermal growth factor (EGF) in the adult male mouse submaxillary gland will be studied by in vitro translation of poly A-containing mRNA from the gland in the wheat germ and rabbit reticulocyle systems. EGF-like proteins will be precipitated by specific antisera to EGF, analysed by electrophoresis under denaturing conditions and compared to the proEGF identified by labeling glands with 35S-cystine. The processing of larger precursors of EGF by stripped pancreatic microsomes and by the EGF-binding protein will be examined. Native proEGF isolated from submaxillary glands will be sequenced by conventional methods. The stability of the high molecular weight complex of EGF will be measured in terms of the dissociation of the trypsin-like subunit and the effect of zinc ion on this stability examined. The ability of EGF to bind to its specific receptors when stabilized in the complex will be examined.